(Kitco News) - Total notional amounts outstanding of over-the-counter derivatives reached $639 trillion as of the end of June, down 1% from end-2011, the Bank for International Settlements said Tuesday.

The decline in value came on the back of a strong U.S. dollar versus key currencies between the end of 2011 and end of June 2012. That reduced the U.S. dollar value of contracts, particularly those denominated in euros, the BIS said.